One thing I’m curious about - When I’m in aero position, the tops of my thighs are touching my chest at the top of the stroke. Is this fairly normal, or am I a bit too low?
If pics are needed, I can probably get some taken soon.
Edited to add: Knees hitting chest must be when I was tired and collapsing the chest. Here’s the video I shot last night (Kind fugly lighting, apologies)
http://www.youtube.com/watch?v=oHXlAt404kc
John
this would be where the whole moving the seat forward thing comes into play =)
.
this would be where the whole moving the seat forward thing comes into play =)
…and possibly shorter cranks. See Slowman’s article on the front page…
this would be where the whole moving the seat forward thing comes into play =)
…and possibly shorter cranks. See Slowman’s article on the front page…
Hrm. I hadn’t thought about that. I’m on a Valdora PHX carbon, size small, with 172.5 cranks. I think I’ll have the wife snap some photos of me riding past the house today, and post them.
Edited to add: Just read the article. Interesting.
John
this would be where the whole moving the seat forward thing comes into play =)
…and possibly shorter cranks. See Slowman’s article on the front page…
Assuming, among other things, that you are willing/able to increase your cadence sufficiently to maintain power output without having to increase the force you must generate. (I wasn’t, at least not when going down from 165 to 148 mm cranks.)
this would be where the whole moving the seat forward thing comes into play =)
…and possibly shorter cranks. See Slowman’s article on the front page…
Assuming, among other things, that you are willing/able to increase your cadence sufficiently to maintain power output without having to increase the force you must generate. (I wasn’t, at least not when going down from 165 to 148 mm cranks.)
Dunno. I run 90-100+ cadence now. I’ve always been more of a spinner than a masher.
Wish I had the time and $$ to come out for the FISTapalooza.
John
John, the question is if you feel you are losing some power, of its causing any back or hip problems. I would try adding a spacer under the stem and see if you feel any difference, but its not necessarily bad to have the knees to the chest if your flexibility is good. I switched from 172.5 to 165 cranks and it helped me with some hip issues. It took me about a month to adapt to the shorter cranks. I couldnt see going as short as Andrew did on his.
Kevin
p.s. Signed up go through the FIST program on March 31!
I couldnt see going as short as Andrew did on his.
I was trying out John Cobb’s ‘low sit’ position:
What were your hip issues that the shorter cranks helped?
John, the question is if you feel you are losing some power, of its causing any back or hip problems. I would try adding a spacer under the stem and see if you feel any difference, but its not necessarily bad to have the knees to the chest if your flexibility is good. I switched from 172.5 to 165 cranks and it helped me with some hip issues. It took me about a month to adapt to the shorter cranks. I couldnt see going as short as Andrew did on his.
Kevin
p.s. Signed up go through the FIST program on March 31!
Well, you know me. You know my flexibility is above the norm.
I don’t feel like I’m losing power, but like everyone, I’m always questioning my fit. And, since this is my first TT bike (even though the seat tube angle on the PHX isn’t steep), I have nothing to compare it against.
I need to bring my bike in anyway, something in the BB goes “klunk” about every 10th revolution or so.
John
Aha!
(even though the seat tube angle on the PHX isn’t steep),
John
Post the pics. Offhand I would say that it’s almost certainly less than optimal if your thighs are hitting your chest.
If you are in a size small frame, you would likely be better off with a shorter crank.
Check to see if you are pointing your toes while at the top of the pedal stroke. That could be a reason you are hitting your chest.
jaretj
Check to see if you are pointing your toes while at the top of the pedal stroke. That could be a reason you are hitting your chest.
jaretj
I know I am slightly. When I first started cycling semi-seriously, “ankling” was the in thing and that’s what I learned. It’s toned down a lot since then, but I know my heel is still slightly higher coming over the top of the stroke.
John
… I think I’ll have the wife snap some photos of me riding past the house today, and post them.
I would suggest that, instead of what you propose above, put the bike on a trainer and have her snap the pics from the front and side WHILE you are pedaling. Even better, if it’s possible, take video and either post the vid or take vid caps and post them.
Trying to get good info out of “paparazzi shots” taken while you ride past the house just doesn’t sound too productive 
… I think I’ll have the wife snap some photos of me riding past the house today, and post them.
I would suggest that, instead of what you propose above, put the bike on a trainer and have her snap the pics from the front and side WHILE you are pedaling. Even better, if it’s possible, take video and either post the vid or take vid caps and post them.
Trying to get good info out of “paparazzi shots” taken while you ride past the house just doesn’t sound too productive
I’ll try both. I don’t really have a good way to get video from the camera to the comp. I know our dig cam has a “burst” mode where it just keeps snapping shots.
One point: On dan’s crank article ( here ), it says that shortening the cranks by 2.5 mm effectively raises your position by 5mm? Am I interpreting that correctly?
John
… I think I’ll have the wife snap some photos of me riding past the house today, and post them.
I would suggest that, instead of what you propose above, put the bike on a trainer and have her snap the pics from the front and side WHILE you are pedaling. Even better, if it’s possible, take video and either post the vid or take vid caps and post them.
Trying to get good info out of “paparazzi shots” taken while you ride past the house just doesn’t sound too productive
I’ll try both. I don’t really have a good way to get video from the camera to the comp. I know our dig cam has a “burst” mode where it just keeps snapping shots.
One point: On dan’s crank article ( here ), it says that shortening the cranks by 2.5 mm effectively raises your position by 5mm? Am I interpreting that correctly?
John
It increases your “clearance” between your leg and your torso by 5mm due to the “pedal circle” diameter being reduced by twice the crank length difference…but your saddle is only raised by 2.5mm (when keeping the same knee flexion angle at the bottom of the stroke). There’s other things to take into account as well to keep your relationship to the bike’s “touchpoints” the same (besides just seat height) that I just listed over here:
http://forum.slowtwitch.com/gforum.cgi?post=2248707;search_string=;#2248707
… I think I’ll have the wife snap some photos of me riding past the house today, and post them.
I would suggest that, instead of what you propose above, put the bike on a trainer and have her snap the pics from the front and side WHILE you are pedaling. Even better, if it’s possible, take video and either post the vid or take vid caps and post them.
Trying to get good info out of “paparazzi shots” taken while you ride past the house just doesn’t sound too productive
I’ll try both. I don’t really have a good way to get video from the camera to the comp. I know our dig cam has a “burst” mode where it just keeps snapping shots.
One point: On dan’s crank article ( here ), it says that shortening the cranks by 2.5 mm effectively raises your position by 5mm? Am I interpreting that correctly?
John
It increases your “clearance” between your leg and your torso by 5mm due to the “pedal circle” diameter being reduced by twice the crank length difference…but your saddle is only raised by 2.5mm (when keeping the same knee flexion angle at the bottom of the stroke). There’s other things to take into account as well to keep your relationship to the bike’s “touchpoints” the same (besides just seat height) that I just listed over here:
http://forum.slowtwitch.com/...rch_string=;#2248707
Yeah, I saw that one too when reading through. Seems to be a lot of crank questions today.
John
“shortening the cranks by 2.5 mm effectively raises your position by 5mm? Am I interpreting that correctly?”
tom has it. the issue is your hip angle at the top of your pedal stroke. this is an important metric, because it determines what sort of leverage you’ll have as you start pushing on the pedals. if you shorten the crank by 2.5mm, you increase the “clearance” between your torso and your thigh by 5mm. you can do whatever you want with this extra clearance. you can use it to increase your armrest drop by 5mm, flattening your back, if it ought to be flatter. or you can give yourself that clearance if you need it, which may or may not be the case with your position.
but you lose torque when you shorten the crank, so you have to make up for this with an extra beat or two (or three) a minute in cadence.
“shortening the cranks by 2.5 mm effectively raises your position by 5mm? Am I interpreting that correctly?”
tom has it. the issue is your hip angle at the top of your pedal stroke. this is an important metric, because it determines what sort of leverage you’ll have as you start pushing on the pedals. if you shorten the crank by 2.5mm, you increase the “clearance” between your torso and your thigh by 5mm. you can do whatever you want with this extra clearance. you can use it to increase your armrest drop by 5mm, flattening your back, if it ought to be flatter. or you can give yourself that clearance if you need it, which may or may not be the case with your position.
but you lose torque when you shorten the crank, **so you have to make up for this with an extra beat or two (or three) a minute in cadence. **
I was hoping you’d touch on this in your article, but I find it helpful to think of this part of the subject more in terms of “tangential foot speed” than in terms of cadence. The way I understand it, your muscles have a preferred range of contraction speed for sustained efforts…so, if you shorten the cranks, that means to keep the “foot speed” (i.e. muscle contraction rate) the same, the cadence needs to increase since each foot is traveling a shorter distance (i.e. the circumference) per revolution. Everything after that is just gearing